
124 Testing
a \
(TN-C-S) together with the adjustments to measurements necessary in
order to compensate for the normal neutral currents, make this test
unpopular.
The test instruments for both tests are connected as shown in
Diagram 93.
Insulation resistance tests
In order to ensure that the cable insulation is sound and that no live or
neutral earth faults exist on an installation, an insulation resistance test is
carried out. Clearly, the higher the resistance of the insulation between
conductors, and between conductors and earth, the better. The
Regulations recommend a minimum value of
1
megohm (ΜΩ).
Diagram 93 (a) Live-earth test; (b) neutral-eart ...